Many computer applications, such as those involving interactive media and scientific computation, require reading of data at a data rate of about 5 MB/sec. While the technology permits some components of disk drives, such as read heads, to operate at data rates of 30 MB/sec., it is not currently possible for the electronic components of a read channel. Techniques heretofore proposed cannot be used for low-end applications, such as with personal computers or notebooks, which require low power consumption.
In a read channel, a read head (inductive or magnetoresistive) generates an analog signal from data stored in binary form on a disk. Each change in orientation of the binary data results in a peak in the analog signal. The electronic components of the read channel must reliably detect the peaks in the analog signal in order to reconstruct the binary data.
In a channel using peak detection, a peak is detected (1) if the signal changes its sign, (2) if it exceeds a threshold, and (3) if its derivative is zero. The peak detection approach provides an analog channel with low power consumption that is relatively inexpensive to manufacture but requires reliable detection at each peak. However, reliable detection cannot be guaranteed in high data rate applications where overlap of the signal response can occur between enabling peaks.
Published European Patent Application 0 463 752 A2 discloses a pattern-matching circuit which compares bit by bit a given multibit data lo pattern against templates of various multibit patterns and then outputs as the most likely multibit pattern that one which most closely matches the given pattern.
U.S. Pat. No. 4,945,538 discloses a signal processing channel which processes an analog read signal after it is converted by an analog-to-digital converter into digitized sample values.
No prior art of which applicants are aware discloses a signal processing channel in which a run-length-limited (RLL)-encoded analog read signal is integrated and weighted by a preselected set of staircase amplifier gain factors to provide a plurality of staggered analog signals, each of which is constant for an identical preselected period of time (such as a half-bit period) but offset timewise in equal increments for detecting multibit patterns instead of single bits.